One method of forming double-toothed belts has been to injection mold the belt from a suitable material, such as polyurethane. Many applications, however, require the use of rubber and the injection molding process is not suitable for such belt manufacture.
One improved method of forming a double-toothed belt is illustrated in U.S. Pat. No. 4,589,941 of Tanaka et al., which patent is owned by the assignee hereof. As disclosed therein, a double-toothed timing belt is manufactured by forming a preform with teeth on one face thereof. The opposite face of the belt is provided with oppositely projecting teeth in accurate alignment with the firstly formed teeth of the preform by successive molding of pluralities of the opposite teeth to the outer face of the preform, with the preform entrained about a pair of adjustably spaced toothed pulleys. Accurate pitch line difference is maintained by providing shims between the mold and belt support during the molding of the plurality of second sets of teeth to the preform. The outer face of the belt is treated to define a bonding surface, such as by roughening thereof. An unvulcanized rubber insert is placed between the preform outer surface and an outer stretchable fabric layer.